A number of optical methods and systems are readily available for determining the physical attribute of an object such as the dimension of an object or its orientation. In particular, there exists a number of dynamic measuring systems based on the combination of fanned laser beams and digital cameras. A fanned laser beam emits a fan of laser rays, emanating from a centre of the laser, which all lie in a common plane; that is, the plane of the fanned laser, or the “laser plane”. When the fanned laser illuminates a body, the laser rays create a line on an outer surface of the body which is the intersection of the laser plane with the outer surface of the body.
The line created by the fanned laser can be recorded by a digital camera as a two-dimensional image. If the line created by the fanned laser is recorded by a digital camera, and the fanned laser and digital camera are in a fixed position relative to each other, then it can be shown mathematically that each point in the camera's view illuminated by the laser can be resolved into a three dimensional position in any particular co-ordinates, provided the orientation of the laser plane, and the position and orientation of the camera are predefined precisely in co-ordinates related to the body being observed, and provided the camera's optical settings and characteristics are also known.
In industrial applications setting the lasers and cameras into precisely known orientations relative to the body being measured is difficult and sometimes impractical.
An object of the present invention is to provide an optical method for determining a physical attribute of an object utilising fanned lasers and digital cameras which does not require precise mechanical setup of the three dimensional location and orientation of the fanned lasers and digital cameras relative to the moving object.